Electrical resistor



3- 1930- J. F. TRITLE ELECTRICAL RESISTOR Filed June 15, I928 Ihvenf'or I J hn FITriHe, b Wm His ATTorne Patented Dec. 2, 1930 UNITED STATES PATENT OFFICE JOHN F. TRITLE, OF ERIE, PENNSYLVANIA, ASSIGNOR TO GENERAL ELECTRIC CO]!!- PANY, A CORPORATION OF NEW YORK ELECTRICAL RESISTOR Application filed June 15,

My invention relates to electrical resistors,

' more particularly to resistors employed in plication in the control of electrical apparatrol of electric cars and locomotives.

tus it has particular application in the Icont. is very desirable in equipments of this character where exceptional vibration occurs, that the electrical resistors employed be of a rigid, strong, and durable construction. It is further desirable that they have large heat radiating surfaces and yet be light in weight. yarious forms of resistors have been proposed as substitutes for the ordinary heavy cast grid, but it has often been found that their lack of rigidity is a serious limitation to their effectiveness since neighboring grids are in danger of coming into contact with each other. For this reason the various forms of stamped grids have been furnished with stilfening'means, as for example, stiffenin'g rods-or wires. These stiffening rods or wires, however, not only increase the cost of construction but also by contacting with the resisting elements decrease their eflective-radiating surfaces. My invention, therefore, contemplates the provision of a resistor in which the advantages of large radiating surfaces are incorporated with those of light,

ri id and economic construction.

11 carrying out my invention in one form thereof, I provide a resistor made up of a plurality of resistance units, each resistance unit of the resistor assembly being provided with an insulated support on which a resistance ribbon is wound into a substantially flat coil with spacedturns, the ribbon having but a very small area 'in contact with the insulated support. I further enhance the rigidity of the unit by providing separate supports for the terminals, the supports not only relieving the unit of the entire terminal load,

' but also permitting ready adjustment of the terminal connections. v

For a more complete understanding of my 1928. Serial No. 285,728

invention, reference should be had to the.

accompanying drawing in which Fig. 1v is a perspective view of the assembled resistor with portions broken away to illustrate certain structural details, Fig. 2 is an expanded view of a portion of the resistor assembly showing the relation between the resistance units and the metallic spacers which serveas terminal supports, Fig. 3 is a diagrammatic representation of the units connected in series, and Fig. 4.- is 'a diagrammatic representat-ion of the' units connected in multiple.

I Referring to the drawing, I have shown my invention in one form as applied to an electrical resistor particularly applicable to car or locomotive control equipment.

shown, the resistor 10 comprises a plurality f of resistance units 11 suitably mounted within a supporting casing 12. The casing 12 comprises metal end plates 13 and a top heat insulating plate '14 made of asbestos composition or the like, the casin 12 being provided with supporting brac ets 15 suitably connected thereto and insulated therefrom by insulators 16.

Referring particularly to Fig. 2, it will be observed that each resistance unit 11 comprises a light, resilient, metal ribbon made of a suitable electrical resistance material such as an alloy of iron, aluminum and chromium. This ribbon is wound into a substantiall flat coil 20 having the form of a flattened elix which has its turns spaced apart so that there is no danger of the various portions of the ribbon coming into contact with each other. Each unit also comprises a suitable insulated support 21 whichis provided for the coil 20, the support 21 being inserted within the coil substantially axially or centrally thereof and being firmly gripped between the lengths forming the various convolutions due to the inherent resiliency of the metal from which the coil is formed. Thus, not only is the coil tween insulatingstrips 23, as for exam lemica strips, which in turn aregrippedetween the convolutions of the coil 20.

A metallic spacer '24, servin not only as a spacer but also as anfelectricaiconductor, as will be explained, :is inserted between each pair of units 11, the-spacers 24 beinginsulat ed from the adjacent coils 20 by. means of suitable insulating strips 25. Thus, the units and spacers are arranged in alternate order within the resistor assembl The upper end of each metallic spacer 24 is provided with a projecting portion 26 suitably apertured to receive an electrical terminal connection.

Referring to Figs. 2 and 3, it will be ob- 'of the coil is connected, as by welding, to the upper end of the spacer 24' positioned at that side of the unit and that the lower terminal ofthe coil is likewise connected to the lower end of the spacer 24 positioned at the other side of the unit. Thus, the adjacent coils 20 are connected in series, the s acers 24 serv ing as electrical conductors etween them. It is pointed out that this construction permits all the terminal load to be carried directly by the spacers 24, all external loads and strains thus being removed from the coils 20. Furthermore, this construction provides additional supporting means for the coils 20 since each coil in addition to being supported by its supporting member 21, which it firmly grips, is supported at its ends by being welded-to the spacers.

In order that the units 11 and the spacers 24 may be supported, and formed into a rigid, compact, assembled construction, the supports 21 and the spacers 24 are provided at each end with an aperture 28 through which suitable insulated, supporting rods 30 may be passed. Referring to Fig. 1, it will be observed that the insulated rods 30 extend throughout the entire length of the resistor assembly and are rigidly secured to the end plates 13 by means of nuts 31. Thus, the units 11 and the spacers 24 are rigidly and compact- "1y mounted'within' the casing 12.

Suitable channel members 33 extend vertically within the casing 10 and are provided with apertures through which the nsulated rods 30 pass, whereby the rigidity of the entire assembly is increased.

It is pointed out that the projecting portions 26 of each of the spacers 24 are at-the top of the resistor assembly, thereby permit ting all of the outside electrical connectionsto be brought in at the top thereof. This construction greatly increasesv the convenience in making various adjustments of resistance.

Although Figs. 2 and 3 illustrate the units 11 connected in series, they may very conveniently be connected in multiple as shown 'cal in each case.

While I have described my invention as embodied in concrete form and as operating in a specific'manner in accordance with the provisions of the patent statutes, it should be understood that I do not limit my invention thereto since various modifications thereof will su gest themselves to those skilled in the art wit out departing from the spirit of my invention the scope of which is set forth in the annexed claims.

. What I claim as new and desire to secure by Letters Patent of the United States is:

1. A resistor assembly comprising a plurality of resistance units, each unit comprising a flattened helix of metal ribbon wound flatwise, an insulating support disposed within said helix and in contact with a relatively small area of the inner surface of said ribbon, insulated metallic spacers between adjacent units to which terminals of the units are con: nected, and means for clamping said helixes, supports, and spacers together to form a rigid assembly. I

2. A resistor assembly comprising a plurality of resistance units, each unit comprising a substantially flat coil, an insulated support surrounded by said coil, insulated metallic spacers between adjacent units to which terminals of the units are connected, the said spacers being adapted to receive external connections at their corresponding ends, and means for clamping said coils, supports, and spacers together to form a rigid assembly. I

3. "A resistor assembly comprising a plurality of resistance units,'each unit comprising a flat helix of metal ribbon wound flatwise, an insulated metallic support disposed within said helix and in contact with a relatively small area of the inner surface of said ribbon, insulated metallic spacers interposed between adjacent units to which terminals of the units are connected, the said spacers and supports being mounted parallel to each other, and means for supporting said helixes, supports and spacers and holding the same in fixed relationship in the resistor assembly.

In witness whereof I have hereunto set my hand this 17th day of Ma 1928.

' J O N F. TRITLE. 

